A dark secret locked up. Song Jihyo is not who everybody thinks she is. Her reputation is the y and ruthless killer, who's the second leader of thterrifying RM gang. But when a new mission that leads her to a school, leaves her astray and lost. School. She hated school. Jihyo hated anything to do with school, but the hardest part of going undercover in a highschool, is to stay unnoticed, and Song Jihyo is somebody who stands out.

Jihyo thinks she's got it all figured out until he comes crashing into her life. He brings love with him. And Jihyo starts to feel. However, being in a gang means risks and that's no easy life. The number one rule in a gang is always the gang first no matter what. With the commander Kim Jongkook as her gang's leader, Kang Gary's seductiveness, Giraffe prying into her life, HaHa's warnings, highschool drama queens hating her, and her family, Jihyo will have to be the ace in everything. 

But the question is, how?